OK got a motor thats a b16 built head and its 12.5-1 compression. So a valve Is bad and we take it to a shop. Get the head back and everything is fine. Aobut 400miles later the motor starts to get hard to turn and stall often. So we start to trouble shoot. While doing so the plugs are replace from ac delcos (dont laugh) to ngk's There for a 2000 si and look the same as the ac's. Well about 3 miles later the motor locks up, we pull the plugs and the have hit the pistons, the plugs are all bent up and tinny marks on the to of the pistons. Also the car is over heating very badly. The machinest did "clean the head up" but now it seems as if he milled it to far. Any ideas.

 

Wrong plugs. Need C-59-C champions or 5238 NGK. Its your job to check that stuff, not the machine shop unless you gave him the block, pistons, etc. and said make sure all this stuff clears. How much was the head milled before? What piston to crown height? Extended plug or recessed plug? Stock head gasket or one of them trick thin ones? What was the piston to deck height clearance? how about piston to head with the hd. gasket you were using? Did you check all that? If not leave the machine shop alone and find out how to do it.

 

ok your missing what im saying. THe car ran fine, all that was checked over. THere was clearance. But one of the valves was not seating so great so we sent the head to the shop. Now we get it back and the plugs hit. only way this could happen is if the head was milled. And all we asked for was it to be cleaned up. But we allso got the head back with the vtech rockers in upside down. SO i guess that should have told us something about the shop

 

WHAT WAS THE PLUG/ PISTON CLEARANCE BEFORE THE CAR WAS DONE?? WAS THE HEAD MILLED ATH THE MACHINE SHOP??? DID U USE THE SAME THICKNESS HEAD GASKET...... YOUR ANSWER IS NGK PART # 6945